| 1. |
- Krishna, Pothula Hari, et al.
(author)
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Multi-band PIFA for combined 3G and DVB-H Terminals : a preliminary study
- 2007
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In: 2007 IEEE International Workshop on Antenna Technology. - Piscataway, NJ : IEEE. - 1424410878 ; , s. 439-442
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Conference paper (peer-reviewed)abstract
- Based on the work by Ciais et. al, a small, efficient and low profile Planar Inverted-F antenna with multi-band operations for the use in mobile telephones has been studied. The antenna was designed using a High Frequency Structure Simulator, HFSS, built and verified. In order to increase the bandwidth of the antenna from the original design it is further optimized by frequency tuning using the shorts of different parasitic element. The resulting antenna operates over two wide bands from (710-1200) MHz and from (1750-2170) MHz, covering five cellular bands and the upper part of the UHF-band allowing it to be used in terminals combining cellular and DVB-H operations.
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| 2. |
- Prasad, Sathyaveer, 1978-, et al.
(author)
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EVALUATION OF THE TELIA SCATTERED FIELD MEASUREMENT METHOD FOR ESTIMATION OF IN-NETWORK PERFORMANCE OF MOBILE TERMINAL ANTENNAS
- 2007
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In: 29th Annual Symposium of the Antenna Measurement Techniques Association (AMTA 2007). - St.Louis,USA : AMTA 2007.
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Conference paper (other academic/artistic)abstract
- In this paper we present and evaluate a method for estimation of in-network performance of mobile terminal antennas developed by the Swedish telecom operator Telia. The Telia Scattered Field Measurement (TSFM) Method is intended to give a better estimate of the performance of the mobile terminal antenna as in an in-network fading scenario. The parameter measured from the TSFM method is referred to as the Scattered Field Measurement Gain, SFMG, i.e. the Mean Effective Gain, MEG, measured relative to a half wave dipole antenna. MEG includes the radiation pattern of the mobile terminal antenna as well as an estimate of polarization and directional losses that occur due to the propagation environment. In this study it is found that the TSFM method provides a good measure of the in-network performance of the mobile terminal antenna. Furthermore, it is shown that the SFMG measured with this method is found to be well correlated with the Total Radiated Power Gain, TRPG, or radiation efficiency. This suggests that the Total Radiated Power, TRP, may be a good measure of the in-network performance of mobile terminal antennas if measured with proper adjustment to the antenna and propagation channel mismatch.
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| 3. |
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| 4. |
- Ramachandran, Prasadh, 1982-, et al.
(author)
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Adaptive Matching Circuitry for Compensation of Finger Effect on Handset Antennas
- 2009
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In: EuCAP 2009. - Berlin. ; , s. 801-804
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Conference paper (peer-reviewed)abstract
- In this paper we present and evaluate the effect of hand on terminal antenna and discuss a method to compensate for the mismatch. A dual band PIFA was used in this study. The presence of the hand was observed to cause 2-6dB loss in efficiency in low-band and 2-4dB loss in highband.In this study we propose a dynamic antenna matching (DAM) technique to improve matching level that can improve the total efficiency of the antenna by 2 – 4dB compared to the mismatched case.
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| 5. |
- Ramachandran, Prasadh, et al.
(author)
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Adaptive penta-band handset antenna with hand effect compensation
- 2012
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In: IET Microwaves, Antennas & Propagation. - : The Institution of Engineering and Technology. - 1751-8725 .- 1751-8733. ; 6:1, s. 79-86
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Journal article (peer-reviewed)abstract
- Theincrease in the number of cellular operating bands and theever-increasing criteria antenna size reduction has pushed the need touse switchable antenna structures. Further, the presence of a handin the close vicinity of the antenna causes deterioration inperformance. The authors present a switchable antenna technique, evaluate theeffect of the human hand on it and discuss anovel method to compensate for the mismatch. A penta-band switchableplanar inverted-F antenna covering 824–960 and 1710–2170 MHz has been usedin this study. The presence of the hand was observedto cause 2.0–6.0 dB loss in efficiency for the low band.Using the proposed extra-ground antenna switching method and the dynamicantenna matching, technique the total efficiency of the antenna canbe improved by 0.5–2.5 dB compared to the mismatched case
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| 6. |
- Ramachandran, Prasadh, 1982-, et al.
(author)
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Impedance determination of terminal power amplifiers for optimal antenna matching using load-pull method
- 2009
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In: 2009 IEEE INTERNATIONAL WORKSHOP ON ANTENNA TECHNOLOGY. - Santa Monica, California : IEEE. - 9781424443963 - 9781424443956 ; , s. 1-4
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Conference paper (peer-reviewed)abstract
- In this paper we present a single tuner based load-pull method for characterization of optimal antenna load impedance in mobile terminals. In the proposed load-pull set-up the mobile terminal itself is used as a source. The presented method can provide valuable data for antenna design since it determines the optimal impedance at the antenna connector/pad taken into account the full output circuitry of the mobile terminal. It reveals the modification of the power amplifier, PA, output impedance caused by the presence of saw filter, antenna switch, and transmission line possibly present between the PA and the antenna. With the presented method it is not only possible to characterize the optimum antenna impedance to present to the terminal in different bands and channels but also to reveal the impedance miss-match sensitivity for each channel.
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| 7. |
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| 8. |
- Ramachandran, Prasadh, 1982-
(author)
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Method and Arrangement for Matching an Antenna
- 2008
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Patent (pop. science, debate, etc.)abstract
- A method and an arrangement for matching the antenna of a radio device in transmitting condition. The antenna impedance in the output of the power amplifier of a transmitter is adjusted by means of a π-shaped reactive matching circuit, the component values of which can be selected from a relatively wide array of the alternatives. The component values are selected by means of the multiple-way switches, which only are located in the transverse branches of the matching circuit. The switches are set (706) by the control unit, input variables of which being the SWR value provided by the directional coupler, the operating band used each time and a value of the transmitting power. The matching is based on an adjusting process to be executed at regular intervals, in which process the control unit tries different combinations of the switch states and finally selects (710) the combina¬ tion, which brings the lowest SWR value. In the beginning of the adjusting process the control unit reduces (705), on grounds of the current values of the input variables, the number of the combinations to be tried. The antenna matching maintains relatively good, although the internal output impedance of the amplifier and the impedance from the output towards the antenna would strive to differ from each other for external reasons, a band changing or a change in the outptut power.
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| 9. |
- Ramachandran, Prasadh, et al.
(author)
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Reconfigurable small antenna for mobile phone using MEMS tunable capacitor
- 2013
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In: 2013 Loughborough Antennas and Propagation Conference, LAPC 2013. - : IEEE. - 9781479900916 ; , s. 354-357
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Conference paper (peer-reviewed)abstract
- In this paper we present a tunable PIFA which can be used in a mobile terminal. A NanoMech™ process enabled MEMS digital variable capacitor has been used as a capacitive load to the antenna. The antenna occupies a volume of just 1.3 cc and is targeted to be placed at the bottom corner of the device. With the help of tunability the antenna is able to cover from 704-960MHz in the low-band and 1710-2170MHz in the high-band, thus covering a wide range of frequency bands required for GSM/WCDMA/LTE systems. The MEMS device has an equivalent series inductance of less than 0.1nH hence the variation in the capacitance value with respect to frequency is less than 10%up to 5GHz. Further, the equivalent series resistance (ESR) of the digital variable capacitor is <0.4 across the whole frequency range of interest, hence causing very low insertion loss to the antenna. The tunable antenna is characterized by measuring it in 3D anechoic chamber. The measured total efficiency of the antenna varies from -4 to -2dB for 700MHz-960MHz and -3dB to -2dB for 1710-2170MHz.
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